influence of a specific group of cells (organizer) on the Differentiation of another group of cells. Mediated by cehmical substances (inducers) passed from the organizer to adjacent cells.

notochord

Made of mesodermal cells. Develop into nervous system.

neural tube

gives rise to the brain and spinal cord (CNS)

neural crest

Cells at the tip of each neural fold that migrate laterally and give rise to many components of peripheral nervous system (PNS)

chorionic villi

Extend into the uterine wall and become closely associated with endometrial cells, developing into the spongy tissue of the placenta

placenta

Site of nutrition, respiration, and waste disposal for the fetus

Fetal hemoglobin

Has a greater affinity for oxygen than adult hemoglobin, tus oxygen preferentially diffuses into fetal blood, metabolic wasters and CO2 diffuse in the opposite direction-- from fetal blood into maternal blood

Circulatory system between mother and fetus

Maternal and fetal blood do not mix. All exchange of material between maternal and fetal blood vessels occurs in the placenta via diffusion.

Immunological protection of placenta

The placenta offers the fetus some immunological protection by PREVENTING the diffusion of foreign matter into fetal blood

Permeability of placenta

Placenta is permeable to viruses, alcohol, and drugs and toxins, but not bacteria.

By which the blood bypasses the fetal liver before convergining with the inferrior vena cava

Blood mixing in fetus

Oxygenated blood from the umbilical vein mixes with deoxygenated blood of the venae cavae, so the blood is only partially oxygenated

foramen ovale

A shunt that diverts blood away from the pulmonary arteries where blood bypasses the pulmonary circulation and enters the left atrium directly from the right atrium.

ductus arteriosus

Remaining blood in right atrium empties into the right ventricle and is pumped into the pulmonary artery and most of this blood is shunted directly from the pulmonary artery to the aorta diverting even more blood away from lungs

Fetus blood in pulmonary arteries

Carries partially oxygenated blood to lungs

Fetal lungs

non functional during development. a small amount of partially deoxygenated blood goes to the fetal lungs to unload further oxygen into the developing lungs. Deoxygenated blood then returns to left atrium via pulmonary veins.

Blood mixing in fetus

deoxygenated blood from lungs mixes with the partially oxygenated blood that crossed over from the right atrium via the foramen ovale before being pumped into the systemic circulation by the left ventricle

umbilical arteris

Retunrs deoxygenated blood from the fetus to the placenta

At birth, forman ovale to closes

Increased left atrial pressure coupled with decreased right atrial pressure causes foramen ovale to close

First trimester of gestation (pregnancy)

Major organs begin to develop

Second trimester of gestation (pregnancy)

Face appears human, toes and fingers elongate

Third trimester of gestation (pregnancy)

Antibodies are transported by highly selective ACTIVE transport from mother to fetus for protection against foreign matter.